Rapid analysis of bacterial composition in prosthetic joint infection by 16S rRNA metagenomic sequencing

Elucidating Causal Relationships Among Gut Microbiota, Human Blood Metabolites, and Knee Osteoarthritis: Evidence from a Two-Stage Mendelian Randomization Analysis

Background: Although previous observational studies suggest a potential association between gut microbiota (GM) and knee osteoarthritis (KOA), the causal relationships remain unclear, particularly concerning the role of blood metabolites (BMs) as potential mediators. Elucidating these interactions is crucial for understanding the mechanisms underlying KOA progression and may inform the development of novel therapeutic strategies. Objective: This study aimed to determine the causal relationship between GM and KOA and to quantify the potential mediating role of BMs. Methods: Instrumental variables (IVs) for GM and BMs were retrieved from the MiBioGen consortium and metabolomics genome-wide association studies (GWAS) databases. KOA-associated single-nucleotide polymorphisms were sourced from the FinnGen consortium. Inverse-variance weighted approach was utilized as the main analytical method for Mendelian randomization (MR) analysis, complemented by MR-Egger, simple mode, weighted mode, and weighted median methods. The causal relationships between GM, BMs, and KOA were sequentially analyzed by multivariate MR. False discovery rate correction was applied to account for multiple comparisons in the MR results. Sensitivity analyses and reverse MR analysis were also conducted to verify the reliability of the findings. Finally, a two-step approach was employed to determine the proportion of BMs mediating the effects of GM on KOA. Results: MR analysis identified seven gut microbial species that are causally associated with KOA. Additionally, MR analysis of 1091 BMs and 309 metabolite ratios revealed 13 metabolites that influence the risk of KOA. Through two-step analysis, three BMs were identified as mediators of the effects of two GMs on KOA. Among them, 6-hydroxyindole sulfate exhibited the highest mediation percentage (10.26%), followed by N-formylanthranilic acid (6.55%). Sensitivity and reverse causality analyses further supported the robustness of these findings. Conclusion: This research identified specific GMs and BMs that have a causal association with KOA. These findings provide critical insights into how GM may influence KOA risk by modulating specific metabolites, which could be valuable for the targeted treatment and prevention of KOA.

Pathogen Detection in Spinal Infections: Next-Generation Sequencing Versus Conventional Microbiological Methods

OBJECTIVE AND BACKGROUND

Early and accurate diagnosis of spinal infections, including spinal tuberculosis, is pivotal for effective treatment but remains challenging. This study aims to assess the diagnostic yield of metagenomic next-generation sequencing (mNGS) compared with that of conventional microbiological tests (CMTs) in identifying pathogens associated with spinal pathologies, with a special focus on infections leading to surgical interventions.

METHODS

We enrolled 85 patients who underwent spinal surgery, comprising 63 patients with clinically diagnosed spinal infections, including patients with spinal tuberculosis, and 22 patients with noninfectious spinal conditions. The procedures involved irrigation and debridement for persistent wound drainage, with subsequent DNA extraction from plasma and joint fluid for mNGS and CMT analysis.

RESULTS

Significantly increased C-reactive protein (CRP) levels were observed in patients with infections. The mNGS approach showed greater diagnostic sensitivity (92.06%) for detecting pathogens, including Mycobacterium tuberculosis, than did CMTs (36.51%). Despite its low specificity, mNGS had considerable negative predictive value (70.59%), underscoring its utility in ruling out infections.

CONCLUSIONS

The mNGS offers superior sensitivity over CMTs in the diagnosis of a variety of spinal infections, notably spinal tuberculosis. This study highlights the potential of mNGS in enhancing the diagnosis of complex spinal infections, thereby informing targeted treatment strategies.

Exploring the Microbial Landscape of Bone and Joint Infections: An Analysis Using 16S rRNA Metagenome Sequencing

Background

Bone and joint infections (BJIs) are challenging to diagnose. This study evaluated the utility of 16S rRNA gene sequencing in diagnosing BJIs, comparing it with conventional bacterial culture to explore microbial diversity in orthopedic infections.

Methods

Thirty patients with BJIs were enrolled from January 2019 to September 2020 at a single orthopedic center. Diagnoses were based on the Musculoskeletal Infection Society standards. DNA extraction, 16S rRNA sequencing, and microbial composition analysis were performed. Conventional bacterial culture results were compared with metagenomics detection, and associations with blood routine and biochemical test factors were analyzed.

Results

The study enrolled 30 patients with BJIs. Traditional bacterial culture successfully identified pathogens in 60% (18/30) of cases, predominantly Staphylococcus aureus. In contrast, 16S rRNA metagenomics sequencing revealed distinct microorganisms in all cases, it unveiled a diverse microbial landscape. The correlation between bacterial culture and metagenomics detection showcased both concordance and discrepancies. Consistency of detection between the two methods showed that metagenomics detection detected the same genus or species in 14 (87.5%) of the 16 samples identified as species by bacterial culture. In nearly half of the patients with negative cultures, pathogenic microorganisms were detected, highlighting the capability of 16S rRNA sequencing to identify microorganisms, even in samples with negative or unidentified culture results. Moreover, no significant correlation was observed between bacterial culture, metagenomics detection and the factors of blood routine and biochemical test.

Conclusion

This study deepens our understanding of the microbial complexity in BJIs. While traditional culture methods are cost-effective and practical, 16S rRNA gene sequencing proves valuable for complementary microbial analysis, particularly when traditional methods fail or rapid identification is critical. This emerging diagnostic approach can enhance the accuracy and speed of pathogen identification, enabling more effective interventions in the management of BJIs.

Are Red Blood Cell Distribution Width and Platelet Count Useful for Diagnosing Periprosthetic Joint Infection in Patients Undergoing Re-Revision Arthroplasty

OBJECTIVE

Accurate and prompt identification of periprosthetic joint infections (PJIs) is critical prior to re-revision arthroplasty to ensure optimal surgical outcomes. Among routinely measured blood indices, red blood cell distribution width (RDW) and platelet count (PLT) have shown strong correlations with infection presence. This study aimed to assess the utility of RDW and PLT for diagnosing PJI in patients scheduled for re-revision arthroplasty.

METHODS

This retrospective research encompassed all patients who underwent re-revision hip or knee arthroplasty at our institution from 2008 to 2022. Participants were categorized into either the PJI (n = 41) or the non-PJI (n = 47) group following the guidelines established in the 2013 International Consensus Meeting on PJI. In this analysis, RDW and PLT counts were evaluated alongside conventional inflammatory markers, including C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). The efficacy of these diagnostics was evaluated by the area under the receiver operating characteristic (ROC) curve ([area under the curve AUC]).

RESULTS

RDW demonstrated a modest AUC of 0.678 with sensitivity at 61.0% and specificity at 71.7%, using a threshold of 14.5%. PLT was on par with ESR, showing an AUC of 0.773, and both sensitivity and specificity around 73% at a threshold of 201 × 109/L. CRP presented the highest diagnostic accuracy with an AUC of 0.815, achieving a sensitivity of 82.9% and specificity of 73.9% at a 6.9 mg/L threshold, surpassing ESR's AUC of 0.754. None of the biomarkers, individually or combined, outperformed CRP alone (p > 0.05).

CONCLUSIONS

In the context of re-revision arthroplasty, RDW and PLT demonstrate limited efficacy as diagnostic biomarkers for PJI. However, CRP retains its reliability as a biomarker when the diagnostic threshold is appropriately recalibrated.

Potentially pathogenic culturable bacteria in hemodialysis waters

BACKGROUND

Hemodialysis patients are at risk of acquiring healthcare-related infections due to using non-sterile water to prepare hemodialysis fluid. Therefore, microbiological control and monitoring of used water are of crucial importance.

MATERIALS AND METHODS

In this work, we identified bacterial populations occupying a hemodialysis water distribution system for almost a 6-month period in Ahvaz city, southwest of Iran. A total of 18 samples from three points were collected. We found high colony counts of bacteria on R2A agar. 31 bacteria with different morphological and biochemical characteristics were identified by molecular-genetic methods based on 16 S rRNA gene sequencing. Endotoxin concentrations were measured, using Endosafe® Rapid LAL Single-Test Vials.

RESULTS

A diverse bacterial community was identified, containing predominantly Gram-negative bacilli. The most frequently isolated genus was Sphingomonas. Five species including M. fortuitum, M. lentiflavum, M.szulgai, M. barrassiae, and M. gordonae was identified .Despite the presence of Gram-negative bacteria the endotoxin analysis of all samples revealed that their endotoxin values were below the detection limit.

CONCLUSION

The members of Sphingomonas genus along with Bosea and mycobacteria could be regarded as pioneers in surface colonization and biofilm creation. These bacteria with others like Pelomonas, Bradyrhizobium, staphylococcus, and Microbacterium may represent a potential health risk to patients under hemodialysis treatment.

Enhancing Pathogen Detection in Implant-Related Infections through Chemical Antibiofilm Strategies: A Comprehensive Review

Implant-related infections (IRIs) represent a significant challenge to modern surgery. The occurrence of these infections is due to the ability of pathogens to aggregate and form biofilms, which presents a challenge to both the diagnosis and subsequent treatment of the infection. Biofilms provide pathogens with protection from the host immune response and antibiotics, making detection difficult and complicating both single-stage and two-stage revision procedures. This narrative review examines advanced chemical antibiofilm techniques with the aim of improving the detection and identification of pathogens in IRIs. The articles included in this review were selected from databases such as PubMed, Scopus, MDPI and SpringerLink, which focus on recent studies evaluating the efficacy and enhanced accuracy of microbiological sampling and culture following the use of chemical antibiofilm. Although promising results have been achieved with the successful application of some antibiofilm chemical pre-treatment methods, mainly in orthopedics and in cardiovascular surgery, further research is required to optimize and expand their routine use in the clinical setting. This is necessary to ensure their safety, efficacy and integration into diagnostic protocols. Future studies should focus on standardizing these techniques and evaluating their effectiveness in large-scale clinical trials. This review emphasizes the importance of interdisciplinary collaboration in developing reliable diagnostic tools and highlights the need for innovative approaches to improve outcomes for patients undergoing both single-stage and two-stage revision surgery for implant-related infections.

A prospective multicentre evaluation of BioFire® Joint Infection Panel for the rapid microbiological documentation of acute arthritis

OBJECTIVES

To assess the performance of the rapid syndromic BioFire® Joint Infection Panel (BF-JIP) to detect bacterial and fungal pathogens, as well as antibiotic resistance genes, directly in synovial fluid specimens collected from patients with acute arthritis.

METHODS

The study was conducted in six French bacteriological laboratories. To assess the performances of BF-JIP, results were compared with those of synovial fluid 14-day culture and, in case of discrepancy, with those of complementary molecular methods and intraoperative samples. A total of 308 synovial fluid specimens were tested after collection from 308 adults and children presenting with clinical and biological suspicion of acute arthritis; patients presenting with acute periprosthetic joint infection were included according to the European Bone and Joint Infection Society 2021 criteria.

RESULTS

Only one specimen failed (no result). On the basis of the consolidated data, the BF-JIP was concordant with the 14-day culture in 280 (91.2%) of the 307 specimens finally included in the study. The positive percentage agreement was 84.9% (95% CI, 78.8-89.8%) and the negative percentage agreement was 100% (95% CI, 97.2-100%). The positive predictive value was extremely high (100%; 95% CI, 97.6-100%), whereas the negative predictive value was lower (82.6%; 95% CI, 75.7-88.2%), partially explained by the missing target species in the panel.

DISCUSSION

The BF-JIP showed high performances to detect pathogens involved in acute arthritis.

Serum procalcitonin has no significance in the diagnosis of periprosthesis joint infection before total hip and knee replacement

Background

Currently, there is no "gold standard" for early diagnosing PJI. The diagnosis of periprosthetic joint infection (PJI) is a challenging problem in the clinic. As we know, many serum markers have been used in the early diagnosis of PJI. The aim of this study was to validate the value of PCT in the diagnosis of PJI.

Methods

A retrospective review of 77 patients with revision arthroplasties from January 2013 to July 2020 was conducted. PJI was defined using the modified Musculoskeletal Infection Society (MSIS) criteria combined with follow-up results. Besides medical history, clinical and laboratory data was gathered. Preoperative blood was taken for serum PCT and other biomarkers measurement. Receiver operating characteristic (ROC) curves were generated to evaluate the biomarkers' diagnostic performance and optimal cut-off value.

Results

Forty-one patients were identified as the PJI group (27 hips and 14 knees), while thirty-six patients were identified as the aseptic loosening (AL) group (33 hips and 3 knees). The AUCs for C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), Platelets (PLT), Fibrinogen (FIB), and Procalcitonin (PCT) were 0.845 (95% CI 0.755-0.936, p < 0.001), 0.817 (95% CI 0.718-0.916, p < 0.001), 0.728 (95% CI 0.613-0.843, p < 0.001), 0.810 (95% CI 0.710-0.910, p < 0.001) and 0.504 (95% CI 0.373-0.635, p = 0.950), respectively. Higher Area under the Curve (AUC) values were obtained for the combinations of PCT and CRP (AUC = 0.870) (95% CI, 0.774-0.936), PCT and ESR (AUC = 0.817) (95% CI, 0.712-0.896), PCT and PLT (AUC = 0.731) (95% CI, 0.617-0.825), PCT and FIB (AUC = 0.815) (95% CI, 0.710-0.894). The serum PCT indicated a sensitivity of 19.51% and a specificity of 83.33% for diagnosing PJI. When the optimal cut-off value for PCT was set as 0.05 ng/ml, its positive and negative likelihood ratios were 57.1% and 47.6%, respectively.

Conclusion

In conclusion, serum PCT appeared to be no reliable biomarker in differentiating PJI from aseptic loosening before revision arthroplasties. However, PCT combined with other biomarkers further increases the diagnostic accuracy.

Human Knee Has A Distinct Microbiome: Implications for Periprosthetic Joint Infection

INTRODUCTION

Pathogens causing prosthetic joint infection are thought to gain access to the knee during surgery or from a remote site in the body. Recent studies have shown that there is a distinct microbiome in various sites of the body. This prospective study, and first of its kind, was set up to investigate the presence of possible microbiome in human knee and compare the profile in different knee conditions.

METHODS

This transversal study prospectively obtained synovial fluid from 65 knees (55 patients) with various conditions that included normal knee, osteoarthritis, aseptic revision, and those undergoing revision for periprosthetic joint infection (PJI). The contralateral knee of patients who had a PJI were also aspirated to compare the composition of the PJI knee with uninfected contralateral knee. A minimum of 3 milliliters (ml) of synovial fluid was collected per joint. Then, the samples were aliquoted for culture and next generation sequencing (NGS) analysis.

RESULTS

The highest number of species was found in native osteoarthritic knees (P≤0.035). Cutibacterium, Staphylococcus, and Paracoccus species were dominant in native non-osteoarthritic knees, and meanwhile a markedly high abundance of Proteobacteria was observed in the osteoarthritic joints. Moreover, the contralateral and aseptic revision knees showed a similar trend in bacterial composition (P=0.75). The NGS analysis of patients who had PJI diagnosis, confirmed the culture results.

DISCUSSION/CONCLUSION

Distinct knee microbiome profiles can be detected in patients who have osteoarthritis and other knee conditions. The distinct microbiome in the knee joint and the close host-microbe relationships within the knee joint may play a decisive role in the development of osteoarthritis and periprosthetic joint infection.

Promising applications of D-amino acids in periprosthetic joint infection

Due to the rise in our aging population, a disproportionate demand for total joint arthroplasty (TJA) in the elderly is forecast. Periprosthetic joint infection (PJI) represents one of the most challenging complications that can occur following TJA, and as the number of primary and revision TJAs continues to rise, an increasing PJI burden is projected. Despite advances in operating room sterility, antiseptic protocols, and surgical techniques, approaches to prevent and treat PJI remain difficult, primarily due to the formation of microbial biofilms. This difficulty motivates researchers to continue searching for an effective antimicrobial strategy. The dextrorotatory-isoforms of amino acids (D-AAs) are essential components of peptidoglycan within the bacterial cell wall, providing strength and structural integrity in a diverse range of species. Among many tasks, D-AAs regulate cell morphology, spore germination, and bacterial survival, evasion, subversion, and adhesion in the host immune system. When administered exogenously, accumulating data have demonstrated that D-AAs play a pivotal role against bacterial adhesion to abiotic surfaces and subsequent biofilm formation; furthermore, D-AAs have substantial efficacy in promoting biofilm disassembly. This presents D-AAs as promising and novel targets for future therapeutic approaches. Despite their emerging antibacterial efficacy, their role in disrupting PJI biofilm formation, the disassembly of established TJA biofilm, and the host bone tissue response remains largely unexplored. This review aims to examine the role of D-AAs in the context of TJAs. Data to date suggest that D-AA bioengineering may serve as a promising future strategy in the prevention and treatment of PJI.

A case for investment in clinical metagenomics in low-income and middle-income countries

Clinical metagenomics is the diagnostic approach with the broadest capacity to detect both known and novel pathogens. Clinical metagenomics is costly to run and requires infrastructure, but the use of next-generation sequencing for SARS-CoV-2 molecular epidemiology in low-income and middle-income countries (LMICs) offers an opportunity to direct this infrastructure to the establishment of clinical metagenomics programmes. Local implementation of clinical metagenomics is important to create relevant systems and evaluate cost-effective methodologies for its use, as well as to ensure that reference databases and result interpretation tools are appropriate to local epidemiology. Rational implementation, based on the needs of LMICs and the available resources, could ultimately improve individual patient care in instances in which available diagnostics are inadequate and supplement emerging infectious disease surveillance systems to ensure the next pandemic pathogen is quickly identified.

Polymicrobial Infections and Biofilms: Clinical Significance and Eradication Strategies

Biofilms are population of cells growing in a coordinated manner and exhibiting resistance towards hostile environments. The infections associated with biofilms are difficult to control owing to the chronicity of infections and the emergence of antibiotic resistance. Most microbial infections are contributed by polymicrobial or mixed species interactions, such as those observed in chronic wound infections, otitis media, dental caries, and cystic fibrosis. This review focuses on the polymicrobial interactions among bacterial-bacterial, bacterial-fungal, and fungal-fungal aggregations based on in vitro and in vivo models and different therapeutic interventions available for polymicrobial biofilms. Deciphering the mechanisms of polymicrobial interactions and microbial diversity in chronic infections is very helpful in anti-microbial research. Together, we have discussed the role of metagenomic approaches in studying polymicrobial biofilms. The outstanding progress made in polymicrobial research, especially the model systems and application of metagenomics for detecting, preventing, and controlling infections, are reviewed.

Combination of C-reactive protein and fibrinogen is useful for diagnosing periprosthetic joint infection in patients with inflammatory diseases

BACKGROUND

The screening of periprosthetic joint infection (PJI) in patients with inflammatory diseases before revision arthroplasty remains uncertain. Serum C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), plasma fibrinogen (FIB), monocyte/lymphocyte ratio, and neutrophil/lymphocyte ratio (NLR) can help screening PJI, but their values in patients with inflammatory diseases have not been determined.

METHODS

Patients with inflammatory diseases who underwent revision hip or knee arthroplasty at West China Hospital, Sichuan University, from January 2008 to September 2020 were divided into infected and non-infected groups based on the 2013 International Consensus Meeting criteria. Sensitivity and specificity of the tested biomarkers for diagnosing infection were determined based on receiver operating characteristic (ROC) curves, and optimal cutoffs were determined based on the Youden index. The diagnostic ability of these biomarkers was re-assessed after combining them with each other.

RESULTS

A total of 62 patients with inflammatory diseases were studied; of them 30 were infected. The area under the ROC curve was 0.813 for CRP, 0.638 for ESR, 0.795 for FIB, and 0.656 for NLR. The optimal predictive cutoff of CRP was 14.04 mg/L with a sensitivity of 86.2% and a specificity of 68.7%, while FIB had a sensitivity of 72.4% and a specificity of 81.2% with the optimal predictive cutoff of 4.04 g/L. The combinations of CRP with FIB produced a sensitivity of 86.2% and specificity of 78.1%.

CONCLUSION

CRP with a slightly higher predictive cutoff and FIB are useful for screening PJI in patients with inflammatory diseases, and the combination of CRP and FIB may further improve the diagnostic values.

TRIAL REGISTRATION

ChiCTR.org.cn, ChiCTR2000039989.

16S ribosomal RNA-depletion PCR and its application in cause analysis of yogurt package shrinkage

Fermentative bacteria, the main microbiota in yogurt, interfere with the detection of unintended bacterial contaminants. The removal of fermentative bacteria and enrichment of unintended bacterial contaminants is a challenging task in bacterial detection. The present study developed a new 16S rRNA-depletion PCR for such enrichment and detection. Specifically, a single-guide RNA was designed and synthesized based on the 16S rRNA sequence of Streptococcus thermophilus, with the highest DNA abundance in the yogurt. The CRISPR-Cas9 system was used to specifically cleave and remove the genomic DNA of the fermentative bacteria, followed by PCR amplification. This method improved the detection sensitivity, simplified the operation steps, and reduced the detection cost of PCR analysis. We also used the 16S rRNA-depletion PCR to amplify and detect the unintended bacterial contaminants in yogurts with shrunken packages and analyzed the underlying reasons to prevent this issue of product quality.

Diagnosis and Treatment of Culture-Negative Periprosthetic Joint Infection

Identification of the causative organism(s) in periprosthetic joint infection (PJI) is a challenging task. The shortcomings of traditional cultures have been emphasized in recent literature, culminating in a clinical entity known as "culture-negative PJI." Amidst the growing burden of biofilm infections that are inherently difficult to culture, the field of clinical microbiology has seen a paradigm shift from culture-based to molecular-based methods. These novel techniques hold much promise in the demystification of culture-negative PJI and revolutionization of the microbiology laboratory. This article outlines the clinical implications of culture-negative PJI, common causes of this diagnostic conundrum, established strategies to improve culture yield, and newer molecular techniques to detect infectious organisms.

A Journey into Animal Models of Human Osteomyelitis: A Review

Osteomyelitis is an infection of the bone characterized by progressive inflammatory destruction and apposition of new bone that can spread via the hematogenous route (hematogenous osteomyelitis (HO)), contiguous spread (contiguous osteomyelitis (CO)), and direct inoculation (osteomyelitis associated with peripheral vascular insufficiency (PVI)). Given the significant financial burden posed by osteomyelitis patient management, the development of new preventive and treatment methods is warranted. To achieve this objective, implementing animal models (AMs) of infection such as rats, mice, rabbits, avians, dogs, sheep, goats, and pigs might be of the essence. This review provides a literature analysis of the AMs developed and used to study osteomyelitis. Historical relevance and clinical applicability were taken into account to choose the best AMs, and some study methods are briefly described. Furthermore, the most significant strengths and limitations of each species as AM are discussed, as no single model incorporates all features of osteomyelitis. HO's clinical manifestation results in extreme variability between patients due to multiple variables (e.g., age, sex, route of infection, anatomical location, and concomitant diseases) that could alter clinical studies. However, these variables can be controlled and tested through different animal models.

The Screening of Fixation-Related Infection in Patients Undergoing Conversion Total Hip Arthroplasty after Failed Internal Fixation of Hip Fractures: A Single-Central Retrospective Study

Objective

To evaluate the diagnostic values of preoperative plasma fibrinogen and platelet count for screening fixation‐related infection (FRI) in patients undergoing conversion total hip arthroplasty (cTHA) after failed internal fixation of hip fractures.

Method

This was a single‐center retrospective study. Data were retrospectively analyzed for 435 patients who underwent cTHA in our hospital from January 2008 to September 2020. They were divided into infected (n = 30) and non‐infected groups (n = 405) according to the 2013 International Consensus Meeting (ICM) criteria. The diagnostic sensitivity and specificity of plasma fibrinogen and platelet count were determined using receiver operating characteristic (ROC) curves. Optimal predictive cutoffs of these two markers were determined based on the Youden index. In addition, the diagnostic value of preoperative serum C‐reactive protein (CRP) and erythrocyte sedimentation rate (ESR) for screening FRI were also evaluated based on the cutoffs recommended by the 2013 ICM Criteria. Finally, the diagnostic ability of various combinations of the plasma fibrinogen and platelet count as well as serum CRP and ESR was re‐assessed.

Results

The numbers of patients with and without FRI were 30 (6.9%) and 405 (93.1%), respectively. Areas under the ROC curves were 0.770 for fibrinogen, 0.606 for platelet, 0.844 for CRP and 0.749 for ESR. The optimal predictive cutoff of fibrinogen was 3.73 g/L, which gave sensitivity of 60.0% and specificity of 90.5%. The optimal predictive cutoff for platelet was 241.5 × 10⁹/L, which gave sensitivity of 46.7% and specificity of 83.7%. The CRP gave sensitivity of 66.7% and specificity of 92.5% with the predetermined cutoff of 10 mg/L, while the ESR gave sensitivity of 67.5% and specificity of 72.4% % with the predetermined cutoff of 30 mm/h. The combination of CRP and ESR showed high specificity of 93.2% but low sensitivity of 66.7%, while the corresponding values for CRP with fibrinogen were satisfied both for sensitivity of 80.0% and specificity of 78.7%. The combination of these four biomarkers gave sensitivity of 73.3% and specificity of 85.7%.

Conclusion

Preoperative serum CRP, ESR, plasma fibrinogen and platelet count have low sensitivity on their own for screening FRI in patients, but the combination of CRP with fibrinogen shows promise for that.

Potential Blood Biomarkers for Diagnosing Periprosthetic Joint Infection: A Single-Center, Retrospective Study

Background: Blood biomarkers are first-line tools for identifying periprosthetic joint infection (PJI). C-reactive protein (CRP) is currently recognized as the standard biomarker for PJI diagnosis. Other recently reported novel biomarkers, including plasma fibrinogen, platelet count, monocyte/lymphocyte ratio (MLR), neutrophil/lymphocyte ratio (NLR), and platelet count/lymphocyte ratio (PLR), have also shown promise in diagnosing PJI. This study aimed to evaluate whether these biomarkers were superior to CRP for identifying PJI. Methods: Patients who underwent revision hip or knee arthroplasty at our hospital from January 2008 to September 2020 were included consecutively and divided into infected and non-infected groups according to the 2013 International Consensus Meeting Criteria. Blood samples were collected preoperatively, and erythrocyte sedimentation rate (ESR), CRP, interleukin-6, fibrinogen, platelet count, MLR, NLR, and PLR were analyzed. The diagnostic values of the tested biomarkers and their combinations were compared with CRP based on the area under the receiver operating characteristic curve (AUC) using the z-test. Classification trees were constructed to explore more accurate combinations of the tested markers for identifying PJI. Results: A total of 543 patients were included, of whom 245 had PJI. Among the tested biomarkers, CRP with a cutoff of 7.39 mg/L showed the highest AUC, which gave a sensitivity of 79.1% and specificity of 86.0%. The AUCs of pairwise combinations of tested markers including CRP also were inferior to CRP itself, as were combinations derived from classification trees. Conclusions: Preoperative serum CRP with a low cutoff may be the best reliable blood biomarker for identifying PJI, and those traditional or novel available blood biomarkers could not further improve the diagnostic ability on the basis of CRP.

Nanopore 16S sequencing enhances the detection of bacterial meningitis after neurosurgery

Objective

Nosocomial bacterial meningitis is one of the major complications after neurosurgery. We performed nanopore 16S amplicon sequencing from cerebrospinal fluid (CSF) to evaluate bacterial meningitis in patients who underwent neurosurgery.

Methods

Among the patients who visited the neurosurgery department of Seoul National University Hospital between July 2017 and June 2020, those with clinically suspected bacterial meningitis were included. 16S rDNA PCR was performed from the CSF, and nanopore sequencing was performed for up to 3 h. The reads were aligned to the BLAST database. In each case, the culture and the 16S rRNA gene amplicon analysis were simultaneously performed and compared with each other, and we retrospectively reviewed the medical records. Genuine infection was determined by the identical results between conventional culture study and the sequencing, or clinically determined in cases with inconsistent results between the two methods.

Results

Of the 285 samples obtained from 178 patients who had 16S rDNA PCR, 41 samples (14.4%) were diagnosed with genuine infection. A total of 56.1% (23/41) of the samples with genuine infection showed a false‐negative culture test. In particular, 16S amplicon sequencing was useful in evaluating patients at the initial tests who had infection with intraventricular hemorrhage (Culture false‐negative rate = 100%), subarachnoid hemorrhage (Culture false‐negative rate = 77.8%), and systemic cancer (Culture false‐negative rate = 100%), which are risk factors for central fever. Moreover, 16S amplicon sequencing could suggest the possibility of persistent bacterial meningitis in empirical antibiotic use.

Conclusion

CSF nanopore 16S sequencing was more effective than conventional CSF culture studies in postoperative bacterial meningitis and may contribute to evidence‐based decisions for antibiotic maintenance and discontinuation.

The causal role of gut microbiota in development of osteoarthritis

OBJECTIVE

There is considerable evidence for relationship between gut microbiota and osteoarthritis (OA), but no studies have investigated their causal relationship.

METHOD

This study utilized large-scale genome-wide association studies (GWAS) summary statistics to evaluate the causal association between gut microbiota and OA risk. Specifically, two-sample Mendelian randomization (MR) approach was used to identify the causal microbial taxa for OA. Comprehensively sensitive analyses were performed to validate the robustness of results and novel multivariable MR analyses were further conducted to ensure the independence of causal association. Reverse-direction MR analyses were performed to rule out the possibility of reverse associations. Finally, enrichment analyses were used to investigate the biofunction.

RESULTS

After correction, three microbial taxa were identified to be causally associated with diverse joint OA (P_FDR < 0.100), namely Methanobacteriaceae family for knee OA (P_FDR = 0.043) and any OA (P_FDR = 0.028), Desulfovibrionales order for knee OA (P_FDR = 0.045) and Ruminiclostridium5 genus for knee OA (P_FDR = 0.063). In addition, we also identified five suggestive microbial taxa that were significant with three different methods under the nominal significance (P < 0.05). Sensitive analysis excluded the influence of heterogeneity and horizontal pleiotropy and multivariable MR analysis ruled out the possibility of horizontal pleiotropy of BMI. GO enrichment analysis illustrates the protective mechanism of the identified taxa against OA.

CONCLUSIONS

This study found that several microbial taxa were causally associated with diverse joint OA. The results enhanced our understanding of gut microbiota in the pathology of OA.

Plasma levels of D-dimer and fibrin degradation product are unreliable for diagnosing periprosthetic joint infection in patients undergoing re-revision arthroplasty

Background

The preoperative diagnosis of periprosthetic joint infection (PJI) in patients undergoing re-revision arthroplasty is crucial, so we evaluated whether plasma levels of D-dimer and fibrin degradation product (FDP) could aid such diagnosis.

Methods

We retrospectively analyzed data on patients who underwent re-revision hip or knee arthroplasty at our institute during 2008–2020. Patients were stratified into those who experienced PJI or not, based on 2013 International Consensus Meeting Criteria. Plasma levels of D-dimer and FDP as well as levels of the traditional inflammatory biomarkers C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and interleukin-6 were compared between the groups. The ability of these biomarkers to diagnose PJI was assessed based on the area under the receiver operating characteristic (AUC) curve, for which predictive cut-offs were optimized based on the Youden index.

Results

Based on a cut-off of 0.80 mg/L, D-dimer gave an AUC of 0.595, high sensitivity of 85.7% but poor specificity of 47.8%. Based on a cut-off of 2.80 mg/L, FDP gave an AUC of 0.550, poor sensitivity of 56.5% and poor specificity of 52.9%. CRP, ESR and interleukin-6 showed much better diagnostic ability, with AUCs > 0.82. The combination of CRP and interleukin-6 gave an AUC of 0.877, high sensitivity of 91.7% and acceptable specificity of 78.3%.

Conclusions

Plasma levels of D-dimer and FDP may be inappropriate for diagnosing PJI in patients undergoing re-revision arthroplasty, whereas the combination of serum CRP and interleukin-6 may be effective.

Biofilm microbiome in extracorporeal membrane oxygenator catheters

Despite the formation of biofilms on catheters for extracorporeal membrane oxygenation (ECMO), some patients do not show bacteremia. To elucidate the specific linkage between biofilms and bacteremia in patients with ECMO, an improved understanding of the microbial community within catheter biofilms is necessary. Hence, we aimed to evaluate the biofilm microbiome of ECMO catheters from adults with (n = 6) and without (n = 15) bacteremia. The microbiomes of the catheter biofilms were evaluated by profiling the V3 and V4 regions of bacterial 16s rRNA genes using the Illumina MiSeq sequencing platform. In total, 2,548,172 reads, with an average of 121,341 reads per sample, were generated. Although alpha diversity was slightly higher in the non-bacteremic group, the difference was not statistically significant. In addition, there was no difference in beta diversity between the two groups. We found 367 different genera, of which 8 were present in all samples regardless of group; Limnohabitans, Flavobacterium, Delftia, Massilia, Bacillus, Candidatus, Xiphinematobacter, and CL0-1 showed an abundance of more than 1% in the sample. In particular, Arthrobacter, SMB53, Neisseria, Ortrobactrum, Candidatus Rhabdochlamydia, Deefgae, Dyella, Paracoccus, and Pedobacter were highly abundant in the bacteremic group. Network analysis indicated that the microbiome of the bacteremic group was more complex than that of the non-bacteremic group. Flavobacterium and CL0.1, which were abundant in the bacteremic group, were considered important genera because they connected different subnetworks. Biofilm characteristics in ECMO catheters varied according to the presence or absence of bacteremia. There were no significant differences in diversity between the two groups, but there were significant differences in the community composition of the biofilms. The biofilm-associated community was dynamic, with the bacteremic group showing very complex network connections within the microbiome.

Molecular sequencing technologies in the diagnosis and management of prosthetic joint infections

INTRODUCTION

Prosthetic joint infections (PJIs) can be challenging to eradicate and have high morbidity and mortality. Current microbiology culture methods can be associated with a high false-negative rate of up to 50%. Early and accurate diagnosis is crucial for effective treatment, and negative results have been linked to a greater rate of reoperation.

AREAS COVERED

There has been increasing investigation of the use of next-generation sequencing (NGS) technology such as metagenomic shotgun sequencing to help identify causative organisms and decrease the uncertainty around culture-negative infections. The clinical importance of the organisms detected and their management, however, requires further study. The polymerase chain reaction (PCR) has shown promise, but in recent years multiple studies have reported similar or lower sensitivity for bacteria detection in PJIs when compared to traditional culture. Furthermore, issues such as high cost and complexity of sample preparation and data analysis are to be addressed before it can move further toward routine clinical practice.

EXPERT OPINION

Metagenomic NGS has shown results that inspire cautious optimism - both in culture-positive and culture-negative cases of joint infection. Refinement of technique could revolutionize the way PJIs are diagnosed, managed, and drastically improve outcomes from this currently devastating complication.

Diagnosing fracture related infections: Where are we now?

Accurate diagnosis of fracture related infection (FRI) is critical for preventing poor outcomes such as loss of function or amputation. Due to the multiple variables associated with FRI, however, accurate diagnosis is challenging and complicated by a lack of standardized diagnostic criteria. Limitations with the current gold standard for diagnosis, which is routine microbiology culture, further complicate the diagnostic and management process. Efforts to optimize the process rely on a foundation of data derived from prosthetic joint infections (PJI), but differences in PJI and FRI make it clear that unique approaches for these distinct infections are required. A more concerted effort focusing on FRI has dominated more recent investigations and publications leading to a consensus definition by the American Orthopedics (AO) Foundation and the European Bone and Joint Infection Society (EBJIS). This has the potential to better standardize the diagnostic process, which will not only improve patient care but also facilitate more robust and reproducible research related to the diagnosis and management of FRI. The purpose of this review is to explore the consensus definition, describe the foundation of data supporting current FRI diagnostic techniques, and identify pathways for optimization of clinical microbiology-based strategies and data.

An update about molecular biology techniques to detect orthopaedic implant-related infections

Despite different criteria to diagnose a prosthetic joint infection (PJI), aetiological diagnosis of the causing microorganism remains essential to guide treatment.Molecular-biology-based PJI diagnosis is progressing (faster, higher specificity) in different techniques, from the experimental laboratory into clinical use.Multiplex polymerase chain reaction techniques (custom-made or commercial) provide satisfactory results in clinical series of cases, with specificity close to 100% and sensitivity over 70-80%.Next-generation metagenomics may increase sensitivity while maintaining high specificity.Molecular biology techniques may represent, in the next five years, a significant transformation of the currently available microbiological diagnosis in PJI. Cite this article: EFORT Open Rev 2021;6:93-100. DOI: 10.1302/2058-5241.6.200118.

Think Twice before Prescribing Antibiotics for That Swollen Knee: The Influence of Antibiotics on the Diagnosis of Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) is a rare but devastating complication after total joint arthroplasty. An estimated 7-12% of patients have negative cultures despite clear clinical evidence of infection. One oft-cited reason for this occurrence is the administration of antibiotics in the weeks prior to obtaining cultures. This article reviews the influence of antibiotics on the diagnosis of PJI. Specifically, we examine the effect of prophylactic and therapeutic antibiotic administration on the diagnostic accuracy of microbiological cultures as well as serum and synovial biomarkers. We also explore the potential of molecular techniques in overcoming these limitations in patients who have received antibiotics before specimen collection and propose areas for future research.

Optimizing culture methods according to preoperative mNGS results can improve joint infection diagnosis

AIMS

Metagenomic next-generation sequencing (mNGS) is useful in the diagnosis of infectious disease. However, while it is highly sensitive at identifying bacteria, it does not provide information on the sensitivity of the organisms to antibiotics. The purpose of this study was to determine whether the results of mNGS can be used to guide optimization of culture methods to improve the sensitivity of culture from intraoperative samples.

METHODS

Between July 2014 and October 2019, patients with suspected joint infection (JI) from whom synovial fluid (SF) was obtained preoperatively were enrolled. Preoperative aspirated SF was analyzed by conventional microbial culture and mNGS. In addition to samples taken for conventional microbial culture, some samples were taken for intraoperative culture to optimize the culture method according to the preoperative mNGS results. The demographic characteristics, medical history, laboratory examination, mNGS, and culture results of the patients were recorded, and the possibility of the optimized culture methods improving diagnostic efficiency was evaluated.

RESULTS

A total of 56 cases were included in this study. There were 35 cases of JI and 21 cases of non-joint infection (NJI). The sensitivity, specificity, and accuracy of intraoperative microbial culture after optimization of the culture method were 94.29%, 76.19%, and 87.5%, respectively, while those of the conventional microbial culture method were 60%, 80.95%, and 67.86%, respectively.

CONCLUSION

Preoperative aspirated SF detected via mNGS can provide more aetiological information than preoperative culture, which can guide the optimization and improve the sensitivity of intraoperative culture. Cite this article: Bone Joint J 2021;103-B(1):39-45.

Optimal concentration of ethylenediaminetetraacetic acid as an irrigation solution additive to reduce infection rates in rat models of contaminated wound

AIMS

In wound irrigation, 1 mM ethylenediaminetetraacetic acid (EDTA) is more efficacious than normal saline (NS) in removing bacteria from a contaminated wound. However, the optimal EDTA concentration remains unknown for different animal wound models.

METHODS

The cell toxicity of different concentrations of EDTA dissolved in NS (EDTA-NS) was assessed by Cell Counting Kit-8 (CCK-8). Various concentrations of EDTA-NS irrigation solution were compared in three female Sprague-Dawley rat models: 1) a skin defect; 2) a bone exposed; and 3) a wound with an intra-articular implant. All three models were contaminated with Staphylococcus aureus or Escherichia coli. EDTA was dissolved at a concentration of 0 (as control), 0.1, 0.5, 1, 2, 5, 10, 50, and 100 mM in sterile NS. Samples were collected from the wounds and cultured. The bacterial culture-positive rate (colony formation) and infection rate (pus formation) of each treatment group were compared after irrigation and debridement.

RESULTS

Cell viability intervened below 10 mM concentrations of EDTA-NS showed no cytotoxicity. Concentrations of 1, 2, and 5 mM EDTA-NS had lower rates of infection and positive cultures for S. aureus and E. coli compared with other concentrations in the skin defect model. For the bone exposed model, 0.5, 1, and 2 mM EDTA-NS had lower rates of infection and positive cultures. For intra-articular implant models 10 and 50 mM, EDTA-NS had the lowest rates of infection and positive cultures.

CONCLUSION

The concentrations of EDTA-NS below 10 mM are safe for irrigation. The optimal concentration of EDTA-NS varies by type of wound after experimental inoculation of three types of wound. Cite this article: Bone Joint Res 2021;10(1):68-76.

Is D-dimer a reliable biomarker compared to ESR and CRP in the diagnosis of periprosthetic joint infection?

Aims

The diagnosis of periprosthetic joint infection (PJI) has always been challenging. Recently, D-dimer has become a promising biomarker in diagnosing PJI. However, there is controversy regarding its diagnostic value. We aim to investigate the diagnostic value of D-dimer in comparison to ESR and CRP.

Methods

PubMed, Embase, and the Cochrane Library were searched in February 2020 to identify articles reporting on the diagnostic value of D-dimer on PJI. Pooled analysis was conducted to investigate the diagnostic value of D-dimer, CRP, and ESR.

Results

Six studies with 1,255 cases were included (374 PJI cases and 881 non-PJI cases). Overall D-dimer showed sensitivity of 0.80 (95% confidence interval (CI) 0.69 to 0.87) and specificity of 0.76 (95% CI 0.63 to 0.86). Sub-group analysis by excluding patients with thrombosis and hyper-coagulation disorders showed sensitivity of 0.82 (95% CI 0.70 to 0.90) and specificity of 0.80 (95% CI 0.70 to 0.88). Serum D-dimer showed sensitivity of 0.85 (95% CI 0.76 to 0.92), specificity of 0.83 (95% CI 0.74 to 0.90). Plasma D-dimer showed sensitivity of 0.67 (95% CI 0.60 to 0.73), specificity of 0.58 (95% CI 0.45 to 0.72). CRP showed sensitivity of 0.78 (95% CI 0.72 to 0.83), specificity of 0.81 (95% CI 0.72 to 0.87). ESR showed sensitivity of 0.68 (95% CI 0.63 to 0.73), specificity of 0.83 (95% CI 0.78 to 0.87).

Conclusion

In patients without thrombosis or a hyper-coagulation disorder, D-dimer has a higher diagnostic value compared to CRP and ESR. In patients with the aforementioned conditions, D-dimer has higher sensitivity but lower specificity compared to ESR and CRP. We do not recommend the use of serum D-dimer in patients with thrombosis and hyper-coagulation disorders for diagnosing PJI. Serum D-dimer may perform better than plasma D-dimer. Further studies are needed to compare serum D-dimer and plasma D-dimer in arthroplasty patients.

Cite this article: Bone Joint Res 2020;9(10):701–708.

Metagenomic next-generation sequencing of synovial fluid demonstrates high accuracy in prosthetic joint infection diagnostics: mNGS for diagnosing PJI

Aims

The aim of this study was to evaluate the performance of metagenomic next-generation sequencing (mNGS) in detecting pathogens from synovial fluid of prosthetic joint infection (PJI) patients.

Methods

A group of 75 patients who underwent revision knee or hip arthroplasties were enrolled prospectively. Ten patients with primary arthroplasties were included as negative controls. Synovial fluid was collected for mNGS analysis. Optimal thresholds were determined to distinguish pathogens from background microbes. Synovial fluid, tissue, and sonicate fluid were obtained for culture.

Results

A total of 49 PJI and 21 noninfection patients were finally included. Of the 39 culture-positive PJI cases, mNGS results were positive in 37 patients (94.9%), and were consistent with culture results at the genus level in 32 patients (86.5%) and at the species level in 27 patients (73.0%). Metagenomic next-generation sequencing additionally identified 15 pathogens from five culture-positive and all ten culture-negative PJI cases, and even one pathogen from one noninfection patient, while yielding no positive findings in any primary arthroplasty. However, seven pathogens identified by culture were missed by mNGS. The sensitivity of mNGS for diagnosing PJI was 95.9%, which was significantly higher than that of comprehensive culture (79.6%; p = 0.014). The specificity is similar between mNGS and comprehensive culture (95.2% and 95.2%, respectively; p = 1.0).

Conclusion

Metagenomic next-generation sequencing can effectively identify pathogens from synovial fluid of PJI patients, and demonstrates high accuracy in diagnosing PJI.

Cite this article: Bone Joint Res 2020;9(7):440–449.

The value of calprotectin in synovial fluid for the diagnosis of chronic prosthetic joint infection

Aims

This study aimed to evaluate calprotectin in synovial fluid for diagnosing chronic prosthetic joint infection (PJI) .

Methods

A total of 63 patients who were suspected of PJI were enrolled. The synovial fluid calprotectin was tested by an enzyme-linked immunosorbent assay (ELISA). Laboratory test data, such as ESR, CRP, synovial fluid white blood cells (SF-WBCs), and synovial fluid polymorphonuclear cells (SF-PMNs), were documented. Chi-squared tests were used to compare the sensitivity and specificity of calprotectin and laboratory tests. The area under the curve (AUC) of the receiver operating characteristic (ROC) curve was calculated to determine diagnostic efficacy.

Results

The median calprotectin level was 776 μg/ml (interquartile range (IQR) 536.5 to 1132) in the PJI group and 54.5 μg/ml (IQR, 38.75 to 78.25) in the aseptic failure (AF) group (p < 0.05). Using a threshold of 173 ug/ml, the sensitivity was 95.2%, with a 97.6% specificity, and the AUC was 0.993. The sensitivity of calprotectin of the antibiotic-treated PJI group was 100% versus 90.9% of the non-antibiotic-treated PJI group. Although 47.6% (ten cases) of the patients in the PJI group received antibiotics before aspiration, the diagnostic efficacy of calprotectin was not affected. The sensitivity and specificity of ESR, CRP, SF-WBCs, and SF-PMNs ranged from 76.2% to 90.5% and 64.3% to 85.7%, respectively.

Conclusion

Calprotectin in synovial fluid has great diagnostic efficacy for PJI diagnosisand outperformed ESR, CRP, SF-WBCs, and SF-PMNs.

Cite this article: Bone Joint Res 2020;9(8):450–457.

Gut microbiome and osteoporosis: a review

Osteoporosis (OP) is a chronic metabolic bone disease characterized by the decrease of bone tissue per unit volume under the combined action of genetic and environmental factors, which leads to the decrease of bone strength, makes the bone brittle, and raises the possibility of bone fracture. However, the exact mechanism that determines the progression of OP remains to be underlined. There are hundreds of trillions of symbiotic bacteria living in the human gut, which have a mutually beneficial symbiotic relationship with the human body that helps to maintain human health. With the development of modern high-throughput sequencing (HTS) platforms, there has been growing evidence that the gut microbiome may play an important role in the programming of bone metabolism. In the present review, we discuss the potential mechanisms of the gut microbiome in the development of OP, such as alterations of bone metabolism, bone mineral absorption, and immune regulation. The potential of gut microbiome-targeted strategies in the prevention and treatment of OP was also evaluated.

Cite this article: Bone Joint Res 2020;9(8):524–530.

Plasma Fibrinogen and Platelet Count Are Referable Tools for Diagnosing Periprosthetic Joint Infection: A Single-Center Retrospective Cohort Study

BACKGROUND

Although the MusculoSkeletal Infection Society has suggested a series of markers to diagnose periprosthetic joint infection (PJI), no single marker can accurately identify infection before revision hip or knee arthroplasty, and exploring promising markers to easily and reliably diagnose PJI is ongoing. The aim of this study was to evaluate the diagnostic value of plasma fibrinogen and platelet count for diagnosing PJI.

METHODS

We retrospectively included 439 patients who underwent revision arthroplasty from January 2008 to December 2018; 79 patients with coagulation-related comorbidities were evaluated separately. The remaining 360 patients constituted 153 PJI and 207 non-PJI patients. Receiver operating characteristic curves were used to evaluate the maximum sensitivity and specificity of the tested markers.

RESULTS

The receiver operating characteristic curves showed that the areas under the curve for plasma fibrinogen, platelet count, and serum C-reactive protein and erythrocyte sedimentation rate were 0.834, 0.746, 0.887, and 0.842, respectively. Based on Youden's index, the optimal predictive cutoffs for fibrinogen and platelet count were 3.57 g/L and 221 × 10⁹/L, respectively. The sensitivity and specificity, respectively, were 68.6% and 86.0% (fibrinogen) and 57.5% and 83.1% (platelet count) for diagnosing PJI. The sensitivity and specificity, respectively, were 76.7% and 72.2% (fibrinogen) and 48.8% and 63.9% (platelet count) for diagnosing PJI in patients with coagulation-related comorbidities.

CONCLUSION

Plasma fibrinogen performed well for diagnosing PJI before revision arthroplasty, and its value neared that of traditional inflammatory markers. Although the diagnostic value of the platelet count was inferior to traditional markers, its diagnostic value was fair for diagnosing PJI. Fibrinogen also may be useful for diagnosing PJI in patients with coagulation-related comorbidities.

Synovial Fluid Interleukin-16 Contributes to Osteoclast Activation and Bone Loss through the JNK/NFATc1 Signaling Cascade in Patients with Periprosthetic Joint Infection

Because of lipopolysaccharide (LPS)-mediated effects on osteoclast differentiation and bone loss, periprosthetic joint infection (PJI) caused by Gram-negative bacteria increases the risk of aseptic loosening after reimplantation. Synovial fluid interleukin-16 (IL-16) expression was higher in patients with PJI than in patients without joint infection. Thus, we explored the effects of IL-16 on bone. We investigated whether IL-16 modulates osteoclast or osteoblast differentiation in vitro. An LPS-induced bone loss mice model was used to explore the possible advantages of IL-16 inhibition for the prevention of bone loss. IL-16 directly activated p38 and c-Jun N-terminal kinase (JNK)/mitogen-activated protein kinase (MAPK) signaling and increased osteoclast activation markers, including tartrate-resistant acid phosphatase (TRAP), cathepsin K, and nuclear factor of activated T cells 1 (NFATc1). IL-16 directly caused monocytes to differentiate into TRAP-positive osteoclast-like cells through NFATc1 activation dependent on JNK/MAPK signaling. Moreover, IL-16 did not alter alkaline phosphatase activity or calcium deposition during osteoblastic differentiation. Finally, IL-16 inhibition prevented LPS-induced trabecular bone loss and osteoclast activation in vivo. IL-16 directly increased osteoclast activation through the JNK/NFATc1 pathway. IL-16 inhibition could represent a new strategy for treating infection-associated bone loss.